There is known a technique that transmits an intention of a driver of a first vehicle to a driver of a second vehicle in a situation that requires vehicles to give way to each other.
Patent literature 1 discloses such technique of a first vehicle cutting in ahead of another second vehicle for a lane change. Here, the driver of the first vehicle tries to cut in ahead of the second vehicle and thus notifies the driver of the second vehicle of an intention trying to cut in ahead of the second vehicle by operating a turn signal lamp of the first vehicle.
In response, the driver in the second vehicle notifies the driver of the first vehicle of an intention permitting the first vehicle to cut in ahead of the second vehicle, by maintaining a cut-in space without acceleration of the second vehicle or increasing a cut-in space with deceleration of the second vehicle.